Some high speed serial I/O transmitters utilize de-emphasis or pre-emphasis circuits. Such high speed serial implementations can include systems designed in accordance with the PCI (Peripheral Component Interconnect) Express™ Base Specification Revision 1.1, dated Mar. 28, 2005, Serial Advanced Technology Attachment (ATA) systems and others. In at least some of these implementations, the finite output impedance of the current source used in current-mode drivers can result in varying current depending on the voltage on the output of the current source. This can produce higher current in de-emphasized bits and lower current in normalized or pre-emphasized bits. Therefore, the output common-mode for de-emphasized bits is at a lower level as compared with the normalized or pre-emphasized bits. For advanced fabrication processes such as 90 nm and beyond, the output impedance of the current source is further reduced. The mismatch in the output common-mode results in large common-mode noise. In some instances, this large common-mode noise can exceed that which is allowed or desirable in view of certain high speed serial interface applications.